In the 1800s, the North embraced industrialization while the economy of the South continued to depend largely on slave ownership. So, like you guessed, it's not

In the 1800s, the North embraced industrialization while the economy of the South continued to depend largely on slave ownership. So, like you guessed, it's not quite race hatred; more like race superiority. Slaveowners didn't hate black people, they liked them a lot, and wanted them to keep working for free. The North was going to take away their free labor, and the folks with money and power in the South didn't quite like that. My guess is that race hatred came later, when the white slaveowners saw their former slaves succeed in business, education, etc., while their former plantations rotted.